1. Field of Invention
The present invention relates to a lighting device in a motor vehicle.
2. Description of Related Art
Light conductor arrangements are known in the art for use with light functions in motor vehicles. The term “light function” may refer to the front area of the motor vehicle, for example in the realization of an indicator light, a day time running light, or a position light, as well as to the rear area of the motor vehicle, such as in the realization of a brake light, a rear light, an indicator light, a fog light, or a reverse light. The shape of a light conductor can be freely chosen, taking the requirements for the total internal reflection of the light in the light conductor into account, so that there is a great creative variety in the design of the lighting devices, in particular in the shape of the light output areas. Hereby, the objective is to achieve a relatively bright and particularly homogeneously illuminated light output area, despite the design varieties. The light that is coupled into the light conductor is usually produced using semiconductor light sources, preferably light emitting diodes (LEDs), whereby the light can be emitted by one single light emitting diode. However, it is also possible to use several light emitting diodes, for example, in the form of light emitting diode arrays.
Different kinds of light conductor types are known in the related art. Substantially rod-shaped light conductors are used with a cross-section that is preferably circular or elliptical, where the light incidence area is generally arranged on one end face on a free end of the light conductor. At least part of the circumferential surface of the light conductor forms the boundary surface for the total internal reflection and directs the coupled-in light along the longitudinal extension of the light conductor. Moreover, light coupling-out areas (which reflect incident light onto them into the direction of a light output area) can be arranged within the light conductor so that light can be emitted out of the light conductor through the output area. Depending on the design and arrangement of the light coupling-out areas of the light conductor, the light output area can be arranged either on one end face on a free end that is opposite of the first free end, or the light output area can extend alongside at least part of the longitudinal extension of the light conductor. With such elongated light conductors, it is problematic to homogeneously illuminate the light output area which extends at least over part of the longitudinal extension.
Plate-shaped light conductors are also known in the art, and are sometimes referred to as “block” optics, which generally include two walls arranged opposite to each other at a certain distance and which serve as boundary surfaces. Narrow sides of the block optics are usually arranged orthogonal towards the boundary surfaces. At least a first section of the narrow sides serves as a light coupling-out area. Another section of the narrow sides of the block optics, in particular a section located at least partially opposite of the first section, serves as a totally reflective side area. Further sections of the narrow sides between the first and the other section can serve as additional boundary surfaces for a total internal reflection of the coupled-in light. When viewed from above, the contour of the block optics can be arranged in almost any suitable way, and can be adapted to the optical requirements for the block optics. Thus, the block optics can be formed, by way of non-limiting example, as rectangular, round, elliptical, or parabolic at least in a partial section. The contour can essentially follow any free-form. Further, a block optics is advantageous in that it can be used for producing a large, homogeneously illuminated area, and allows for a particularly efficient coupling-in of the light emitted from the light source. Further, coupling-in sections designed in a different manner are similarly conceivably, whereby light can be coupled into the block optics.
In the block optics, a light incidence area can be arranged in a deepening within the plate-shaped element for the light that is being emitted by the light source, which is arranged into one of the boundary surfaces that are located opposite of each other. The deepening can accommodate the semiconductor light source. At least part of the wall of the deepening serves as light incidence area. In a parabolic alignment of the block optics contour, when viewed from above, the light source or the deepening is preferably arranged within the focal point of the parabola. To that end, basically parallel light is emitted out of the block optics via the light coupling-out area. Such a block optics is known from EP 2169296 A1, which includes a plate-shaped transparent element with a parabolic form or a parabolic-like form, when viewed from above. However, this block optics can only achieve the desired homogeneous illumination of the light coupling-out area if it is designed in an even way, formed as an even plate. In such a case, the light coupling-out area is essentially arranged in a rectangular way. If the block optics is designed in a curved shape, in the shape of a hollow cylinder section or of a spherical segment, then the light in the block optics, which is propagated towards the light coupling-out area is pushed towards the outer one of the two oppositely located walls with regards to the curving, so that a particularly bright area results on the outer area of the light coupling-out area. Thus, in a curved or spherical block optics, the illuminated light coupling-out area features the shape of a ring segment. Thus, it is not possible to achieve a homogeneous illumination of the total light coupling-out area with a curved or spherical block optics. Therefore, the known block optics cannot be used, or can only be partially used to accomplish ring-shaped or ring section-shaped illumination areas (for example, to create light rings which surround a light module or a lens of a projector module, or of curved or arched illumination areas in the lighting device).
Thus, the objective of the invention is to provide a lighting device or a light conductor arrangement that can achieve an illuminated light coupling-out area that is as homogeneous as possible, for mainly straight light coupling-out areas, but also for any curved or arched light coupling-out areas.